The subject of the invention is a pneumatic impact tool designed particularly for cleaning castings in foundries.
There is known a pneumatic hammer, as per Polish patent specification No: 128491, fitted with a casing inside of which is mounted a working cylinder in the form of a pipe and fitted with a ram which moves in the sleeve along its axis. This hammer is also fitted with a sealing sleeve fixed in the hammer casing on level with the air inlets that open into the working cylinder. The sleeve closes the air inlets when the working cylinder is at its rest point.
The design shown in this patent doesn't provide a sufficient degree of vibroisolation to comply with vibration standards in force.
The pneumatic hammer as per Polish patent specification No: 122477 has the same disadvantages.
Another hammer design is shown in Polish patent specification No: 122381. This hammer includes a vibroisolator with a negative elastic compensation having a narrow performance range of vibro-isolation. Thus, it cannot be miniaturized as would be required for use within hand-held tools.
There are known other designs of pneumatic hammer tools with reaction damping and fitted with force transformers, as per Polish patent specifications No: 115085 and No: 118242. In these designs, the mass of the tool body acts as a transforming mass, i.e., as a force transformer. The body is divided into two working chambers: one of them--a ram chamber, the other one--a piston rod chamber. The piston rod chamber is under permanent air pressure. Air is led to the ram's working chamber through two passages: one of them being between the ram and the working tool, the other one--between the piston rod and the ram.
The air distribution and feeding of each chamber with air as per the above-mentioned patent is very difficult to realize in production processes. The necessary synchronization of movements of all the masses is disturbed by the striker and the material being worked on that irregularly affects the hammer's casing. Moreover, the need for an additional transformer and chambers precludes the hammer from being shorter.